The invention relates to apparatus and method for purging a pulverizing system of contaminant residue.
An impact mill pulverizes material into fine powders in the range of about 45 microns or less in size. An integral classifier is used to reject oversize particles for the purpose of re-introducing oversized material to the grinding chamber for further processing.
Referring to FIG. 1, a prior art impact mill powderizer and classifier 10 includes a high speed rotor disk 12 with impactors 14, e.g., pins, for pulverizing material, and a rotatably driven classifying wheel 16 for rejecting oversize particles.
In use, material is introduced to powderizer/classifier 10 through a feed inlet tube 18. The material is pulverized by rotating impactors 14. The pulverized product is then swept upward in a column of air and exposed to classifying wheel 16. Fine particles are pulled through the rotating classifier 16 by air flow created by an exhaust fan 20. Oversize particles rejected by classifier 16 are returned into the path of impactors 14 by zone divider 22 for additional size reduction. Particle size is adjusted by increasing or decreasing the rotational speed of classifier 16.
Referring to FIG. 2, the fine product particles are drawn into a product collector 32 where the fine product particles are separated from the air flow.
A powderizing assembly includes a mill for pulverizing material, a main product line, and a purge line including a cyclone separator. Periodically the mill is cleared of all material which is sent through the purge line with residual solids being removed by the cyclone separator.
According to one aspect of the invention, a powderizing assembly includes a product line for receiving product sized powderized material from a powderizing mill, and a purger assembly for receiving non-product sized material from the mill. Non-product sized material is periodically removed from the mill and fed to the purger assembly.
Embodiments of this aspect of the invention may include one or more of the following features.
The purger assembly includes a purge line in parallel with the product line for receiving material from the mill. A first valve is operable to direct material from the mill to one of the product line or the purge line. The first valve and a second valve are operable to isolate the product line from the purge line. The purger assembly includes a cyclone separator and a filter. Alternatively, the purger assembly includes a filter/collector and a fan downstream of the filter/collector.
The powderizing assembly includes the powderizing mill for powderizing the material, a filter/collector downstream of the product line and the purger assembly, and a fan downstream of the product line and the purger assembly.
According to another aspect of the invention, a purger assembly includes a purge line configured to be placed in communication with a powderizing mill for removing residue material from the mill. The purge line includes a cyclone separator.
Embodiments of this aspect of the invention may include one or more of the following features.
The purge line includes a filter. The purge line includes a first valve operable to direct material from the mill to the purge line. The purger assembly includes a filter/collector downstream of the cyclone separator, and a fan downstream of the cyclone separator.
According to another aspect of the invention, a purger assembly includes a purge line configured to be placed in communication with a powderizing mill for removing residue material from the mill. The purge line including a filter/collector.
Embodiments of this aspect of the invention may include one or more of the following features.
The purge line includes a valve operable to direct material from the mill to the purge line, and a fan downstream of the filter/collector.
According to another aspect of the invention, a method of purging a powderizing mill includes providing a purger assembly in communication with the powderizing mill, diverting flow from a product line in communication with the powderizing mill to the purger assembly, and interrupting a size classifier of the powderizing mill to allow non-product sized material from the powderizing mill to be fed to the purger assembly.
Embodiments of this aspect of the invention may include one or more of the following features.
The size classifier is periodically interrupted. The size classifier is interrupted based on amperage draw.
The removal of residue from the mill advantageously lessons wear on the mill, and removes a potential source of contamination from the end product, i.e., the residue contains contaminants that can wind up in the end product. By periodically exhausting the offspecification material that is harder to grind, the quality of the end product is beneficiated and the useful life of the machinery is extended.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.